1. Field of the Invention
This invention relates to acyclic machines, and more particularly, to such machines utilizing a plurality of high current density field coils, such as superconducting field coils, and coaxial stacks of rotor disk interleaved with stator disks connected by a drum to form a disk-drum combination acyclic machine.
2. Description of the Prior Art
In my U.S. Patent application Ser. No. 898,923, filed Apr. 21, 1978, now U.S. Pat. No. 4,208,600, issued June 17, 1980, assigned to the instant assignee, and which is incorporated herein by reference thereto, I described a disk-drum type acyclic machine. In such machines, multiple field coils are disposed in spaced, coaxial relationship and are energized to have opposed poles. Such a machine having n field coils, has n stacks of radially-extending rotor mounted circular disks, n stacks of stator mounted circular disks interleaved on a one-for-one basis with the rotor mounted disks, and n-1 axially-extending drums so positioned, that each of the interleaved stacks of rotor mounted and stator mounted circular disks is disposed in axial alignment and concentric with one of the field coils, respectively, and each of the drums is disposed, respectively, at the gap between two adjacent field coils and concentric therewith. Such a structure provides for utilization of the portion of the magnetic flux generated by the field coils extending in a direction generally perpendicular to the interleaved disks and also the portion of the magnetic flux extending in a direction generally perpendicular to the drums. This effectively utilized the high intensity magnetic fields which are produced by high current capacity coils.
In marine applications, strict limitations are imposed upon machine magnetic field leakage in the vicinity closely adjacent the machine, since operating personnel are required to work in close proximity to the machine. My instant invention provides a means to limit the external magnetic field of such a high field intensity machine.
Another characteristic of high current density coils is their requirement for cooling, in many applications to cryogenic temperatures. If during operation of the machine the cryogenic coolant were lost, the machine would become inoperable. Therefore, some means is required to provide operability of the cryogenic temperature portion of the machine. Such capability is referred to in marine applications as "take home" capability, i.e., the capability to return unassisted to a repair facility.
Accordingly, a primary object of the instant invention is to provide an easily fabricated, immediately available "take home" capability of an acyclic machine employing high current density cryogenic temperature field coils.
A further object is to provide active shielding around the acyclic machine to maintain the flux density of the magnetic field surrounding the machine within a predetermined maximum level at a given distance from the machine surface.